Optical fiber ribbons containing radiation cured encapsulating materials

ABSTRACT

Optical fiber ribbons comprise at least two optical fiber subunit ribbons encapsulated within a radiation cured encapsulating material. The radiation cured encapsulating material allows separation of the subunit ribbons by hand tearing of the encapsulating material and adheres to the subunit ribbons upon twisting of the optical fiber ribbon. The radiation cured encapsulating material preferably has a tear resistance of less than about 2.20 pounds force and an adhesion force to an underlying surface material of greater than about 0.0044 pounds force.

RELATED APPLICATIONS

The present application is a divisional of application Ser. No.09/701,609 filed Feb. 8, 2001 now U.S. Pat. No. 6,628,866 which is a 371of PCT/US00/08095 filed Mar. 27, 2000, which claims priority under 35U.S.C. § 119 of U.S. application Ser. No. 60/127,425 filed Apr. 1, 1999.

FIELD OF THE INVENTION

The present invention is directed to optical fiber ribbons containingradiation cured encapsulating materials and is directed to radiationcured materials suitable for use, inter alia, as encapsulating materialsfor optical fiber ribbons. The radiation cured encapsulating materialshave an advantageous combination of physical properties, including a lowtear resistance and good adhesion. The radiation cured encapsulatingmaterials in turn provide the optical fiber ribbons with improvedreliability and versatility.

BACKGROUND OF THE INVENTION

New optical fiber technologies are continually being developed toaccommodate increasing demands for band width and other communicationproperties. Optical fiber ribbons have been developed to provideincreased packing densities, improved accessibility and the like. In theU.S. telecommunications industry, 12-fiber ribbons have become astandard while in Japan, 8-fiber ribbons have commonly been employed.Optical fiber ribbons are disclosed, for example, in the Duecker U.S.Pat. No. 5,881,194, the Lochkovic et al U.S. Pat. No. 5,561,730 and theHattori et al U.S. Pat. No. 5,524,164, and by McCreary et al,International Wire and Cable Symposium Proceedings (1998):432-439.

Generally, optical fiber ribbons comprise two or more optical fibersembedded and secured within a matrix material. The optical fibers aretypically arranged in parallel relation substantially within a singleplane. To accommodate increased capacity demands, as many as 24 opticalfibers may be arranged in a single linear array in an optical ribbon. Incertain applications, it is desirable to separate the optical fiberribbon into two or more subunits by splitting the optical ribbon. Toallow such separation, it has been a common practice to provide theoptical fibers which are positioned at the ends of adjacent subunits inside-by-side direct contact with each other, without matrix materialtherebetween. This arrangement offers a convenient separating mechanismfor splitting the optical fiber ribbon into subunits. However, owing tothe small size of the individual fibers, their close proximity to oneanother, and/or the properties of the matrix materials, reliablesplitting of the ribbon into subunits has been difficult as uneventearing or splitting and/or optical fiber damage often results.

Several alternatives have been suggested to provide optical fiberribbons which may be more reliably split into subunit ribbons. Forexample, notches have been provided in optical fiber ribbons along thedesired tear or split line. In practice, the notches provided a weakarea in the ribbon structure and have caused various problems with thehandling integrity of the ribbons. Another alternative has been toprovide modular subunits in an optical fiber ribbon. In this design,individual subunits are formed by embedding and securing a number ofoptical fibers in a matrix material. Two or more subunits are thenembedded in an encapsulant material to form the optical fiber ribboncontaining the modular subunit ribbons. For example, Hattori et aldisclose optical fiber ribbon containing two modular subunit ribbons,each of which contains four optical fibers. The subunit ribbons areembedded and secured within an encapsulating material. Similarly,McCreary et al disclose a 24-fiber modular optical fiber ribbon whichcontains two 12-fiber subunit ribbons. The subunit ribbons are embeddedwithin an encapsulating material to form the 24-fiber optical ribbon.

While the modular type optical fiber ribbon containing subunit ribbonsprovide improvement over nonmodular optical fiber ribbons in variousapplications, the modular optical fiber ribbons typically exhibit one ormore deficiencies in use. For example, during tearing or splitting ofthe modular subunits, uneven tear often occurs, resulting in overhang ofthe encapsulating matrix on one split subunit ribbon and excessiveremoval of encapsulating material on an adjacent subunit ribbon. Theuneven tear or splitting of the encapsulating material can beparticularly disadvantageous when the encapsulating material is providedwith printed identification information and such information is removedfrom one of the subunits by uneven tearing. Previous modular opticalfiber ribbons have also been known to exhibit delamination of theencapsulating material from the subunits, particularly upon the twistingof the optical fiber ribbons which is conventionally encountered incabling applications. In yet additional modular optical fiber ribbons,cracking of the encapsulating material has occurred. Accordingly, theneed remains for providing improved modular optical fiber ribbons whichallow for reliable and even splitting of subunits therefrom and whichexhibit improved handling robustness and resist cracking or delaminationof the encapsulating material.

SUMMARY OF THE INVENTION

Accordingly, it is an object of the present invention to provide opticalfiber ribbons, and particularly to provide optical fiber ribbons of themodular type wherein two or more subunit ribbons are encapsulated withinan encapsulating material. It is an additional object of the presentinvention to provide optical fiber ribbons which overcome disadvantagesof the prior art. It is a more specific object of the invention toprovide optical fiber ribbons which allow reliable tearing or splittingof subunit ribbons and which exhibit robust handling properties andresist cracking and/or delamination of the encapsulating material. It isa further object of the invention to provide radiation curedencapsulating materials for use, inter alia, in modular optical fiberribbons.

These and additional objects are provided by the optical fiber ribbonsand encapsulating materials of the present invention. More particularly,the invention is directed to radiation cured encapsulating materialshaving a low tear resistance and good adhesion to an underlying surface.In a more specific embodiment, the encapsulating materials exhibit atear resistance of less than about 2.20 pounds force and an adhesionforce to an underlying surface of greater than about 0.0044 poundsforce. In further preferred embodiments, the encapsulating material hasa percent elongation at break of at least about 5% and a Young's modulusat 25° C. of at least about 1,000 psi. The present invention is alsodirected to optical fiber ribbons which comprise at least two opticalfiber subunit ribbons encapsulated within a radiation curedencapsulating material, wherein the radiation cured encapsulatingmaterial has a low tear resistance which allows the subunit ribbons tobe separated by hand, i.e., the ribbons exhibit hand separability of thesubunit ribbons, and has robust handling properties, whereby the ribbonsresist delamination and cracking when subjected to twisting. In a morespecific embodiment, the optical fiber ribbons include an encapsulatingmaterial having a tear resistance of less than about 2.20 pounds forceand an adhesion force to an outer surface of each subunit of greaterthan about 0.0044 pounds force. Preferably, the radiation curedencapsulating material in which the optical fiber subunit ribbons areencapsulated has a percent elongation at break of at least about 5% anda Young's modulus at 25° C. of at least about 1,000 psi.

The optical fiber ribbons according to the present invention areadvantageous in that they allow reliable tearing or splitting of subunitribbons therefrom, even by hand, resulting in even tear and preventingoverhang or excessive removal of the encapsulating material in theindividual split subunits. Additionally, the optical fiber ribbons ofthe invention exhibit robust handling properties and may be twisted incabling environments without cracking of the encapsulating material ordelamination of the encapsulating material from the subunit ribbons.

These and additional objects and advantages provided by the opticalfiber ribbons and encapsulating materials of the present invention willbe more fully apparent in view of the following detailed description

BRIEF DESCRIPTION OF THE DRAWING

The following detailed description will be more fully understood in viewof the drawing in which:

FIG. 1 sets forth one embodiment of the optical fiber ribbons of theinvention comprising 8 optical fibers arranged in two subunit ribbonsencapsulated within a radiation cured encapsulating material; and

FIG. 2 sets forth a another embodiment of the optical fiber ribbons ofthe invention comprising 24 optical fibers arranged in two subunitribbons encapsulated within a radiation cured encapsulating material.

DETAILED DESCRIPTION

The present invention is directed to optical fiber ribbons and toradiation cured encapsulating materials for use, inter alia, in opticalfiber ribbons. Preferably, the optical fiber ribbons according to thepresent invention are of the modular type and include at least twooptical fiber subunit ribbons encapsulated within a radiation curedencapsulating material. The optical fiber ribbons may comprise two,three, four, or more subunit ribbons as is desired for a particularapplication. Each optical fiber subunit ribbon in turn preferablycomprises two or more optical fibers embedded and encapsulated within amatrix material. While subunit ribbons comprising four, eight and twelveoptical fibers, respectively, are commonly employed, the number ofoptical fibers in a particular subunit ribbon may be varied as desired.

Typical optical fiber ribbons in accordance with the present inventionare shown in FIGS. 1 and 2. Specifically, FIG. 1 is directed to anoptical fiber ribbon 10 which comprises two subunit ribbons 12encapsulated within an encapsulating material 14. Each subunit ribboncomprises four optical fibers 16 embedded within matrix material 18.Although it is preferred that adjacent subunit ribbons 12 are in contactwith one another at their adjacent edges as shown at 20 in FIG. 1, it isequally within the scope of the invention to space adjacent subunitribbons from one another so that encapsulating material 14 separates theadjacent subunits and prevents the adjacent subunit ribbons fromcontacting one another.

Another embodiment of optical fiber ribbons according to the presentinvention is set forth in FIG. 2. In this embodiment, the optical fiberribbon 100 comprises two subunits indicated at 120. The subunits 120 areencapsulated within encapsulating material 140. Each subunit 120contains twelve optical fibers 160 embedded and secured within a matrix180. The encapsulating material 140 is a thin layer relative to thethickness of the subunit matrix material. Those skilled in the art willrecognize that the thickness of the encapsulating material relative tothe subunit may be varied as desired. In a typical embodiment, thethickness of the encapsulating material may be on the order of fromabout 1 to about 50 microns, preferably from about 5 to about 25microns.

Typically, the optical fibers in each subunit of the optical fiberribbons of the present invention are arranged in parallel fashion andsubstantially within a single plane as shown in FIGS. 1 and 2. However,it is equally within the scope of the present invention to arrange theoptical fibers in other configurations as desirable.

The structure, composition and manufacture of the individual opticalfibers 16 is well known in the art. For example, the optical fibers maybe provided with one or more primary coatings and/or secondary coatingsin accordance with techniques known in the art to protect the underlyingglass fiber from external damaging forces and/or to improve theperformance of the optical fibers. Additionally, the optical fibers mayinclude ink coloring as desired. In a preferred arrangement, each fiberof a subunit ribbon is provided with a different and distinguishingcolor.

Matrix materials suitable for use in the subunit ribbons are also knownin the art. Attention is directed to the Duecker U.S. Pat. No. 5,881,194which discloses suitable matrix materials and which is incorporatedherein by reference. Other matrix materials known in the art are alsosuitable for use in the optical fiber subunit ribbons.

In accordance with an important feature of the optical fiber ribbons ofthe invention, the optical fiber subunit ribbons are encapsulated in aradiation cured encapsulating material having low tear resistance whichallows the subunit ribbons to be separated by hand, and having goodadhesion to the underlying surfaces of matrix material. Preferably, theencapsulating material has a tear resistance of less than about 2.20pounds force and an adhesion force to an outer surface of each subunitof greater than 0.0044 pounds force. This combination of propertiesprovides improved even tearing of the ribbon to obtain separateindividual subunits. This combination of properties also provides robusthandling properties to the optical fiber ribbon In preferredembodiments, the radiation cured encapsulating material further has apercent elongation at break of at least about 5% and a Young's modulusat 25° C. of at least about 1,000 psi to further improve the handlingproperties of the optical fiber ribbons.

The tear resistance of the encapsulating material refers to the maximumtear resistance force and is measured in accordance with ASTM D 1004-66,Standard Test Method for Initial Tear Resistance of Plastic Film andSheeting, which is incorporated herein by reference. This methoddetermines the tear resistance of flexible plastic film and sheeting atvery low rates of loading and measures the force required to initiatetearing. The test film comprises a cured film having a thickness ofabout 0.006-0.007 inch (about 150-175 micron thickness). A suitablecuring unit for curing the film comprises a Fusion Systems or othercomparable curing unit capable of producing either ultraviolet orelectron beam radiation. The dose used to cure the film should be about0.7 joules/cm². The encapsulating materials employed in the presentinvention, when cured, have a tear resistance of less than about 2.20pounds force, and preferably of less than about 1.10 pounds force, andmore preferably less than about 0.44 pounds force.

Additionally, the radiation cured encapsulating material also exhibitsan adhesion force to an underlying surface material on which it iscured, for example the outer surface of a subunit ribbon, of greaterthan about 0.0044 pounds force, preferably greater than about 0.011pounds force, and more preferably greater than about 0.015 pounds force.Adhesion force as employed in the present specification and claims ismeasured using the following procedure. A substrate matrix film is firstprepared by pouring a sample of a substrate matrix liquid on a 0.25 inchthick glass plate. A film applicator capable of producing a filmthickness of approximately 0.006 inches (approximately 150 microns) anda width of at least 5 inches is employed. The plate is either placed ina closed apparatus for purging the oxygen therein down to less than 70ppm or is placed in a curing unit which has been previously purged toless than 70 ppm oxygen. A suitable curing unit comprises a FusionSystems or other comparable curing unit capable of producing eitherultraviolet or electron beam radiation. The dose used to cure the filmshould be about 0.7 joules/cm². The resulting cured substrate film istrimmed longitudinally by approximately ⅛ of an inch on both sides, withcare being taken not to completely delaminate the film from the surfaceof the glass. The liquid encapsulating material is then poured on top ofthe substrate film and, using the same film applicator, a film of theencapsulating material is prepared on top of the substrate film. Theencapsulating film should be approximately 0.003 inches (approximately75 microns) in thickness, and is cured under the same conditions asemployed for the curing of the substrate film. The resulting cured filmsandwich is removed from the glass plate and conditioned for at least 16hours at 23±2° C. and 50±10% relative humidity. After this conditioning,two 1-inch strips are cut lengthwise on a sample cutter which providescut films of a 1-inch width by at least eight inch length. The stripsshould be cut at least ¼ inch from the edges of the film with at least ¼inch between them. An Instron or similar tensile testing machineequipped with a software package capable of calculating an average loadexperienced during testing is used to measure the force necessary toseparate the two materials. The cut film strip should be trimmed to alength of about 7.5 inches, and the top layer is peeled off thesubstrate from the bottom to the top of the film, the top being the areawhere the liquid was poured to form the film, until approximately 4inches remain unseparated. This 4-inch section is used as the testsection. The peeled layer of encapsulating material is secured in theupper grip of the Instron and the exposed substrate tab is secured tothe lower grip. The strip should be in line with the two grips and thetest portion should not touch the upper grip. Instron settingscomprising a gauge length of 3.25 inches, crosshead speed of 20 mm/min,and linear test distance of 1.5 inches are employed. During the test,the software program calculates the average load experienced duringseparation of the two layers. The load experienced will increase to acertain value and then remain relatively constant producing a plateau inthe load versus extension curve. The average load is calculated betweenthe initial portion of this plateau region and the end of the lineartest distance. The calculated load for two strips is averaged andreported as the adhesion force.

Radiation cured encapsulating materials having the aforementionedcombination of tear resistance and adhesion provide the optical fiberribbons with even, reliable tearing of subunit ribbons therefrom, andexhibit robust handling properties. In additional embodiments, theradiation cured encapsulating material further has a percent elongationat break of at least about 5%, preferably at least about 10%, and morepreferably at least about 20%. The percent elongation at break is alsomeasured according to ASTM D 882-95a.

In yet further embodiments, the radiation cured encapsulating materialhas a Young's modulus at 25° C. of at least about 1000 psi, and morepreferably of at least about 3000 psi. It is preferred that the modulusis not greater than about 100,000 psi, and in certain embodiments ispreferred to be in the range of from about 1,000 to about 50,000 psi,preferably in the range of from about 3,000 to about 25,000 psi, andmore preferably in the range of from about 3,000 to about 15,000 psi.The modulus is measured according to ASTM D 882-95a, Standard TestMethod for Tensile Properties of Thin Plastic Sheeting, which isincorporated herein by reference.

In preferred embodiments wherein the optical fiber ribbons exhibitreliable even tear properties and particularly robust handlingproperties, the radiation cured encapsulating material preferably has atear resistance of less than about 1.10 pounds force, a Young's modulusat 25° C. in the range of from about 3,000 to about 25,000 psi, apercent elongation at break of at least about 10%, and an adhesion forceto an outer surface material of each subunit ribbon of greater thanabout 0.011 pounds force. More preferably, the radiation curedencapsulating material has a tear resistance of less than about 0.44pounds force, a Young's modulus at 25° C. in the range of from about3,000 to about 15,000 psi, a percent elongation at break of at leastabout 20%, and an adhesion force to an outer surface material of eachsubunit ribbon of greater than about 0.015 pounds force. Such opticalfiber ribbons exhibit particularly good resistance to delamination fromsubunit ribbons and to encapsulating material cracking, even when theoptical fiber ribbons are subjected to excessive twisting and the like.

The encapsulating material employed in the optical fiber ribbons of thepresent invention is radiation curable in order to facilitate productionof the ribbons in accordance with conventional optical fiber ribbonmanufacturing techniques. The radiation cured encapsulating materialsare formed by radiation curing compositions comprising radiation curablemonomers and oligomers and an effective amount of a photoinitiator forradiation curing the composition upon exposure to curing radiation, forexample ultraviolet radiation, or the like. In a preferred embodiment,the compositions from which the radiation cured encapsulating materialis formed comprise a urethane acrylate or methacrylate oligomer,preferably a polyether-based urethane acrylate oligomer or apolyester-based urethane acrylate oligomer, an acrylated acrylic ormethacrylic oligomer, an epoxy acrylate or methacrylate oligomer, ormixtures thereof. These oligomers are commercially available fromvarious sources. Examples of commercially available materials areEbecryl® 4842, a silicone-modified polyether aliphatic urethanediacrylate oligomer, Ebecryl® 270, a polyether aliphatic urethanediacrylate oligomer, and Ebecryl® 1701, an acrylated acrylic oligomer,all of which are available from the Radcure unit of UCB Chemicals Corp.,Smyrna, Ga., CN 963, 965 and 966, polyester urethane acrylate oligomersavailable from Sartomer, CN 816, 817 and 818, acrylated acrylicoligomers available from Sartomer, and CN 120 and UVE 150, epoxyacrylate oligomers available from Sartomer and Croda Resins,respectively. More preferably, the compositions comprise urethaneacrylate oligomer, and further preferably comprises a polyalkyleneglycol-based urethane acrylate oligomer, and polypropylene glycol-basedurethane acrylate oligomers are particularly preferred.

The compositions further comprise at least one monomer having aplurality, i.e., two or more, of acrylate and/or methacrylate moietiesfor increasing the modulus of the composition to at least the lowerlevel of about 1,000 psi. The monomer may comprise a diacrylate ordimethacrylate, a triacrylate or trimethacrylate, a tetraacrylate ortetramethacrylate, or even a pentaacrylate or pentamethacrylate, ormixtures thereof. Such monomers are well known in the art and include,but are not limited to, alkanediol diacrylates, alkanedioldimethacrylates, alkoxylated derivatives thereof, trimethyloyl propanetriacrylate, alkoxylated derivatives thereof, glycerolalkoxytriacrylates, pentaerythritol-containing acrylates such aspentaerythritol tetraacrylate and dipentaerythritolmonohydroxypentacrylate, neopentyl glycol diacrylate, isocyanurate di-and triacrylate components, cyclohexane dimethanol diacrylates anddimethacrylates, alkoxylated derivatives thereof, bisphenol-Adiacrylates and dimethacrylates, alkoxylated derivatives thereof,melamine acrylate and methacrylate derivatives, tricyclodecanedimethanol diacrylate, alkoxylated derivatives thereof, polyetheracrylates and methacrylates, and the like, and mixtures thereof. In apreferred embodiment, the monomer comprises an isocyanurate monomer.More preferably, the monomer having a plurality of acrylate and/ormethacrylate moieties comprises a triacrylate or a trimethacrylate of anisocyanurate compound. Trifunctional monomers, and particularly atriacrylate of trishydroxyethyl isocyanurate, are preferred.

The radiation curable compositions further comprise a photoinitiator forcuring the composition upon exposure to curing radiation. Numerousphotoinitiators suitable for use in the compositions are known in theart. The compositions according to the present invention areadvantageously UV curable. Examples of photoinitiators suitable for usein the compositions of the present invention include, but are notlimited to, benzoin or alkyl ethers thereof such as the benzophenones,phenyl methyl ketone (acetophenone), substituted acetophenones,anthraquinones, polynuclear quinones, aryl phosphine oxides, disulfidesor benzil. In a preferred embodiment, the photoinitiator comprisesbenzophenone, a substituted or unsubstituted acetophenone, or a mixturethereof, and more preferably comprises a substituted acetophenone.

The oligomer, monomer and photoinitiator may be combined in amountsufficient to provide the desired tear resistance and modulus uponcuring of the composition. In a preferred embodiment, the radiationcurable compositions from which the encapsulating material is formedcomprise from about 30 to about 80 weight percent of a polyether-basedurethane acrylate oligomer, from about 1 to about 40 weight percent of amonomer having a plurality of acrylate or methacrylate moieties, and aneffective amount of a photoinitiator for radiation curing thecomposition upon exposure to curing radiation. In further preferredembodiments, the compositions from which the encapsulating material isformed comprise from about 40 to about 75 weight percent, and morepreferably from about 50 to about 70 weight percent, of thepolyether-based urethane acrylate oligomer, from about 10 to about 30weight percent, and more preferably from about 15 to about 25 weightpercent, of the monomer having a plurality of acrylate or methacrylatemoieties, and from about 0.1 to about 20 weight percent, more preferablyfrom about 1 to about 10 weight percent, of the photoinitiator.

The radiation curable compositions may further include one or morecomponents or additives conventionally employed in radiation curablecompositions. For example, the compositions may further comprise aviscosity-reducing component in an amount sufficient to lower theviscosity of the composition. Various viscosity-reducing components arewell known in the art and are suitable for use in the radiation-curablecompositions for forming the encapsulating materials. Examples of suchcomponents include, but are not limited to, linear and branchedhydrocarbon acrylates and methacrylates, for example stearyl acrylate;stearyl methacrylate; isooctyl acrylate; isooctyl methacrylate; laurylacrylate; lauryl methacrylate; caprolactone acrylate; caprolactonemethacrylate; decyl acrylate; decyl methacrylate; isodecyl acrylate;isodecyl methacrylate; isobornyl acrylate; isobornyl methacrylate;alkoxylated nonylphenol acrylates and methacrylates,dicyclopentenyloxyethyl acrylate and methacrylate, tert-butyl-cyclohexylacrylates and methacrylates, 2-phenoxy ethyl acrylates andmethacrylates, alkoxylated derivatives thereof, urethane monoacrylates,including, but not limited to, the reaction product of butyl isocyanateand hydroxy ethyl acrylate, and mixtures thereof. Of the above, thosehaving straight chain alkyl groups of from 12 to 18 carbon atoms arepreferred. This component may also be used to further reduce the tearresistance of the cured composition or to improve the adhesion of thecured composition to an underlying substrate and, if employed, isincluded in the radiation-curable composition in an amount sufficient tolower the viscosity of the composition and/or to provide suchimprovements to the cured composition. Suitably, this component isincluded in an amount of up to about 30 weight percent, and preferablyin an amount of from about 5 to about 15 weight percent.

Additional adhesion promoters for further improving the adhesion of theencapsulating material to the subunit ribbon matrix materials may alsobe employed if desired. Examples of suitable adhesion promoters include,but are not limited to, organic acid derivatives, for example,beta-carboxy ethyl acrylate, and organo alkoxy silanes, titanates andzirconates. These compounds are suitably employed in amounts up to about5 weight percent.

A further optional component for use in the radiation-curablecompositions comprises a component for reducing the coefficient offriction of the cured encapsulating material and/or for improvingwetting of the encapsulating material to an underlying substrate.Various components are known in the art for reducing the coefficient offriction and/or improving the wetting of cured materials and aresuitable for use in the radiation-curable compositions. Examples of suchcomponents include, but are not limited to, silicon compounds, forexample silicone acrylates or other polyorganosiloxane materials,fluorocarbons, waxes and the like. Such components are suitably employedin an amount of up to about 5 weight percent and more preferably in anamount of from about 0.01 to about 3 weight percent.

The radiation-curable compositions may also include various stabilizersto improve shelf life of the uncured compositions and/or to increasethermal and oxidative stability of the cured compositions. Examples ofsuitable stabilizers include tertiary amines such as diethylethanolamine and trihexylamine, hindered amines, organic phosphates, hinderedphenols, mixtures thereof, and the like. Examples of antioxidants whichare particularly suitable for use in the compositions include, but arenot limited to,octadecyl-3-(3′,5′-di-tert-butyl-4′-hydroxyphenyl)propionate;thiodiethylene bis(3,5-di-tert-butyl-4-hydroxy)hydrocinnamate; andtetrakis[methylene(3.5-di-tert-butyl-4-hydroxyhydrocinnamate)]methane.When a stabilizer is used, it may be incorporated in an amount fromabout 0.1 percent to about 3 weight percent. Preferably it is includedin the range from about 0.25 percent to about 2 weight percent. Apreferred stabilizer is thiodiethylene bis(3,5-di-tert-butyl-4′-hydroxy) hydrocinnamate, such as Irganox 1035,from Ciba-Geigy Corporation, Ardsley, N.Y.

The optical fiber ribbons according to the present invention aregenerally prepared in accordance with techniques known in the art.Broadly, coated and inked fibers are arranged in a desiredconfiguration, preferably substantially planar and parallel, a matrixcomposition is applied about the fibers, and the matrix composition iscured to form a subunit ribbon. The radiation curable composition forforming the encapsulating material is then applied to two or moresubunits arranged in a desired configuration, preferably substantiallyplanar and parallel, and cured to form the modular optical fiber ribbonaccording to the present invention.

Although the radiation-cured encapsulating materials have been discussedherein for use in optical fiber ribbons, one of ordinary skill in theart will appreciate that these compositions may be useful in anyembodiment where it is desirable to coat or bind a flexible substrate.Examples of such substrates include, but are not limited to, glass,metal or plastic.

The following examples exemplify specific embodiments of the materialsand optical fiber ribbons of the present invention. Throughout theexamples and the present specification, parts and percentages are byweight unless otherwise specified.

EXAMPLE 1

In this example, a radiation curable composition is prepared comprisingabout 75.1 parts by weight of a silicone modified polyether aliphaticurethane diacrylate supplied under the commercial designation Ebecryl®4842, about 4.5 parts by weight of a photoinitiator comprising1-hydroxycyclohexyl phenyl ketone supplied under the commercialdesignation Irgacure 184, and about 20.4 parts by weight of triacrylatetrishydroxyethyl isocyanurate. The composition is cured by exposure toultraviolet radiation (0.7 joules/cm²). The composition exhibits lowtear resistance and high adhesion within the ranges of the presentinvention. Similar compositions are prepared wherein a non-siliconemodified polyether aliphatic urethane diacrylate supplied under thecommercial designation Ebecryl® 270 was employed in place of theEbecryl® 4842. The resulting cured compositions similarly exhibit a goodcombination of low tear resistance and high adhesion within the rangesof the present invention.

EXAMPLE 2

In this example, a radiation curable composition comprising thefollowing components in the indicated parts by weight was prepared:

Component Parts by Weight Ebecryl ® 4842 61.5 Trifunctional polyether28.0 acrylate Irgacure 184 4.0 Caprolactone acrylate 5.0 Irganox 10351.0 Silicone acrylate cof reducer 0.5The composition was formed into films (6 mil draw down) and cured withultraviolet radiation (0.7 J/cm²). The resulting cured films wereconditioned for at least 16 hr at 23±2° C. and 50±5% relative humidity,cut to size and subjected to measurement of the tear resistanceaccording to ASTM D-1004-66. The tear resistance of the films was asfollows:

Sample Film Thickness (mils) Tear Resistance (lb-force) 1 6.3 0.280 26.3 0.302Thus, the cured materials exhibited low tear resistance. The curedmaterials were also subjected to measurement of adhesion force accordingto the procedures described above and exhibited an adhesion force to astandard subunit ribbon urethane acrylate-based matrix material of about0.028 pounds force.

The present examples and specific embodiments set forth in the presentspecification are provided to illustrate various embodiments of theinvention and are not intended to be limiting thereof. Additionalembodiments within the scope of the present claims will be apparent toone of ordinary skill in the art.

1. A radiation cured encapsulating material having a tear resistance ofless than about 2.20 pounds force, and adhesion force to an underlyingsurface material of greater than about 0.0044 pounds force, and aYoung's modulus at 25° C. in the range of from about 3000 to about15,000 psi, formed by radiation curing a composition comprising fromabout 40 to about 75 weight percent of polyether-based urethane acrylateoligomer, from about 10 to about 30 weight percent of isocyanuratemonomer having a plurality of acrylate or methacrylate groups, and fromabout 0.1 to about 20 weight percent of the photoinitiator for radiationcuring the composition upon exposure to curing radiation.
 2. A radiationcured encapsulating material as defined by claim 1, having a percentelongation at break of at least about 5%.
 3. A radiation curedencapsulating material as defined by claim 1, wherein thepolyether-based urethane acrylate oligomer comprises a polypropyleneglycol-based urethane acrylate oligomer.
 4. A radiation curedencapsulating material as defined by claim 1, wherein the isocyanuratemonomer comprises a triacrylate of trishydroxyethyl isocyanurate.
 5. Aradiation cured encapsulating material as defined by claim 1, having atear resistance of less than about 1.10 pounds force.
 6. A radiationcured encapsulating material as defined by claim 1, having a tearresistance of less than about 0.44 pounds force.
 7. A radiation curedencapsulating material as defined by claim 1, having a percentelongation at break of at least about 10%.
 8. A radiation curedencapsulating material as defined by claim 1, having a percentelongation at break of at least about 20%.
 9. A radiation curedencapsulating material as defined by claim 1, having a tear resistanceof less than about 1.10 pounds force and a percent elongation at breakof at least about 10%.
 10. A radiation cured encapsulating material asdefined by claim 1, having a tear resistance of less than about 0.44pounds force and a percent elongation at break of at least about 20%.11. A radiation cured encapsulating material as defined by claim 1,wherein the composition further comprises a viscosity-reducing componentin an amount sufficient to lower the viscosity of the composition.
 12. Aradiation cured encapsulating material as defined by claim 1, whereinthe composition further comprises a coefficient of friction reducingcomponent in an amount sufficient to lower the coefficient of frictionof the radiation cured material.
 13. A radiation cured encapsulatingmaterial as defined by claim 1, having an adhesion force to anunderlying surface material of greater than about 0.0 15 pounds force.14. A radiation cured encapsulating material having a tear resistance ofless than about 2.20 pounds force, an adhesion force to an underlyingsurface material of greater than about 0.0044 pounds force, and aYoung's modulus at 25° C. in the range of from about 3000 to about15,000 psi, formed by radiation curing a composition comprising fromabout 50 to about 75 weight percent of polyether-based urethane acrylateoligomer, from about 15 to about 30 weight percent of the isocyanuratemonomer having a plurality of acrylate or methacrylate groups, and fromabout 1 to about 10 weight percent of photoinitiator for radiationcuring the composition upon exposure to curing radiation.
 15. Aradiation cured encapsulating material as defined by claim 14, whereinthe polyether-based urethane acrylate oligomer comprises a polypropyleneglycol-based urethane acrylate oligomer and the isocyanurate monomercomprises a triacrylate of trishydroxyethyl isocyanurate.
 16. Aradiation cured encapsulating material having a tear resistance of lessthan about 2.20 pounds force, an adhesion force to an underlying surfacematerial of greater than about 0.0044 pounds force, and a Young'smodulus at 25° C. in the range of from about 3000 to about 15.000 psi,formed by radiation curing a composition comprising from about 50 toabout 80 weight % of a polyether-based urethane acrylate oligomer, fromabout 15 to about 40 weight % of isocyanurate monomer having a pluralityof acryalte or methacrylate groups, and form about 1 to about 10 weight% of photoinitiator for radiation curing the composition upon exposureto curing radiation.
 17. A radiation cured encapsulating material asdefined by claim 2, having a tear resistance of less than about 1.10pounds force, a percent elongation at break of at least about 10%, andan adhesion force to an underlying surface material of greater thanabout 0.011 pounds force.
 18. A radiation cured encapsulating materialas defined by claim 2, having a tear resistance of less than about 0.44pounds force, a percent elongation at break of at least about 20%, andan adhesion force to an underlying surface material of greater thanabout 0.015 pounds force.